Smoke ventilation

ABSTRACT

The invention provides door and window sensors, which can be incorporated into building pressurisation and depressurisation systems, for use in protecting a building&#39;s escape routes against smoke ingress during a fire.

The present invention relates to smoke ventilation, and in particular topressurisation and depressurisation systems of buildings, which aredesigned to protect escape routes and fire-fighting stairs against smokeingress when the building is on fire. The invention extends to sensors,and in particular to door and window sensors, which can be incorporatedinto such building pressurisation and depressurisation systems. Theinvention extends to building pressurisation and depressurisationsystems incorporating such sensors, and to the uses of these systems inmethods for protecting a building's escape routes against smoke ingressduring a fire.

FIGS. 1 and 2 illustrate two different systems, which are designed toprotect stairwell escape routes (4) and fire-fighting stairs (10, 26) ina building (3, 14) against the ingress of smoke during a fire (28). FIG.1 shows a pressurisation system (1), and FIG. 2 shows a depressurisationsystem (2), each system achieving a similar goal, but in a differentway. For example, the pressurisation system in the building (3) shown inFIG. 1, creates a positive pressure within the protected escape route(i.e. the stairwells, 4) when the building is on fire. This is achievedby blowing air into the escape route (4) by large ventilator fans (22),which may be located on the roof of the building (3). Thus, when thebuilding is on fire, the air that is blown into the stairwell (4)maintains the air velocity across open doors maintaining a differentialto the adjacent spaces, for example in the office and accommodationspaces (12). Furthermore, the resultant lower pressure that is createdon the fire floor (28) ventilates the smoke on that floor, the resultbeing that the smoke is prevented from entering the pressurized space(i.e. the stairwell), thereby protecting the escape routes (4). TheBritish Standard currently requires the velocity of escapinggas/air/smoke across the face of a fire door (8) in a burning building(3) to be at least 2 ms⁻¹. This velocity is such that the pressureproduced on the door is sufficient to prevent the ingress of smoke intothe escape route during a fire, but, importantly, is not so great thatan escaping occupant struggles to open the door.

In contrast to the pressurisation system shown in FIG. 1, thedepressurisation system illustrated in FIG. 2 creates a negativepressure within the stairwell escape route (4) in order to dilute andextract smoke which may enter an escape route on the fire floor. It alsoinduces sufficient air from an escape stairwell (4), which may be usedby occupants escaping from other floors. The building (14) also includesventilator fans (22) on the roof connected to a fan starter panel (24).When the building (14) is not on fire, the depressurisation system is instandby mode. However, when the building is on fire (28), the fire isdetected by smoke detectors on the fire floor, which is then reportedback to a control panel (24). A network of differential pressure sensors(16) provided on each floor controlled by the control panel (24)monitors the air pressure sends the pressure data to a programmablelogic controller (PLC, 30), which controls the speed of the fans (22) tocreate a negative pressure (50 Pa) in the corridor or lobby when doorsare closed (4). This negative pressure prevents the smoke ingressinginto the stairwells. It should be noted that the direction of air in adepressurisation system flows in the same direction as in a buildingfitted with a pressurisation system, and the velocity of escapinggas/air across the face of a fire door (8) in a burning building (3)must again be at least 2 ms⁻¹.

Unfortunately, the use of pressurisation and depressurisation systems,as shown in FIGS. 1 and 2, is known to be difficult for controllingsmoke ventilation when a building (3, 14) is on fire (28). In a firescenario, a building behaves like a living body, “breathing” air in andout. Accordingly, ventilating smoke from the building (3, 14), and inparticular the escape routes (4) and fire-fighting stairs (26), can bevery difficult. The design, installation and commission ofpressurisation and depressurisation systems is a notoriously difficultjob for a fire engineer. To date, optimum results are achieved usingpressure differential sensors, which detect the air pressure around thebuilding, but there are various problems associated with using suchsensors.

Firstly, pressure sensors are slow to detect the difference in pressurecaused by the opening and closing of fire doors, as people escape, orthe fire service tackle the fire. This delay in sensing the pressure(and changes in the pressure) can cause difficulty in commissioning thepressurisation or depressurisation system and can become dangerous infire conditions. Secondly, as described in the paper entitled“Performance Assessment of pressurized stairs in high rise buildings” byC. Bellido, A. Quiroz & J. L Torero, page 9, when more than one firedoor is opened, pressurisation and depressurisation systems struggle tomaintain the pressure level in the staircase about the desired set-point(i.e. creating a velocity of escaping air across the face of a fire doorof 2 ms⁻¹) and so pressures can widely fluctuate. As such, the use ofpressure sensors in pressurisation and depressurisation systems isneither rapid nor safe.

There is therefore a need to provide improved pressurisation anddepressurisation systems for protecting escape routes and fire-fightingshafts against smoke ingress when a building is on fire, which are fast,accurate and stable.

According to a first aspect of the invention, there is provided abuilding pressurisation or depressurisation apparatus for ventilating abuilding, the apparatus comprising sensing means for detecting theposition of at least one door or window in the building, and controlmeans for controlling the air leakage in an escape route of the buildingbased on the position of the at least one door or window detected by thesensing means.

In a second aspect, there is provided use of the apparatus according tothe first aspect, for ventilating a building, preferably ventilatingsmoke therein.

In a third aspect, there is provided a method of ventilating a building,the method comprising:

-   -   (i) detecting the position of at least one door or window in the        building, and    -   (ii) controlling the air leakage in an escape route of the        building based on the position of the at least one door or        window detected in step (i).

Advantageously, the apparatus of the invention can be used forventilating an escape route in the building to protect it against smokeingress when the building is on fire. The inventors studied the use ofair pressure sensors in prior art pressurisation and depressurisationsystems, and realized that the air pressure in the stairwell depends, inpart, on the fire doors/windows themselves, due to their variableleakage rate which is largely dependent upon the door/window positions.Accordingly, the inventors realized that it should be possible tocontrol the degree of ventilation caused by a pressurisation ordepressurisation system based on the position (or proximity) of a dooror window in a stairwell, rather than on the air pressure, as measuredby a pressure sensor, as is currently the case. To this end, a series ofcontact and non-contact door and window position sensors have beendeveloped, which are highly responsive, fast and cost-effective comparedto the use of pressure sensors, which are currently used inpressurisation and depressurisation systems.

In one embodiment, the sensing means may be a door position sensor. Inanother embodiment, the sensing means may be a window position sensor.The door or window, the position of which is detected by the sensingmeans, may be located where it can influence the ingress of smoke intothe building's escape route during a fire. For example, the door orwindow may be located in an internal wall or partition of the building.Thus, the door or window may be an internal door or window. The door orwindow may be a hinged or sliding door or window. The door may be a firedoor.

Preferably, the sensing means is capable of being attached to a door orwindow frame, preferably a door lintel. The sensing means may compriseone or more fixing means for attachment to the window frame or lintel.For example, the sensing means may be arranged to be secured to a lintelsuch that the mid-point of the sensing means is substantially alignedwith hinges of the door or window. Advantageously, this alignment of thesensing means with the hinges ensures that any movement of the door orwindow can be easily and accurately detected. The sensing means ispreferably arranged, in use, to detect a 180° swing of the door orwindow with respect to the frame, in embodiments where the door orwindow is hinged. In embodiments where the position of a sliding door orwindow is detected, however, the sensing means may be attached to thedoor frame, and aligned with the direction in which the door or windowslides.

The sensing means may be capable of producing an output in the form of0V-10V, or 4 mA to 20 mA. Advantageously, as shown in FIG. 3, the outputof one embodiment of the sensing means is substantially linear withrespect to the position of the door or window, which makes its use inthe pressurisation or depressurisation apparatus both fast and accurate.The sensing means may rely upon contact with the door or window todetermine is position with respect to its frame. Alternatively, thesensing means may not rely on contact with the door or window, and maybe referred to as a non-contact sensor.

In a first embodiment, one example of which is described in Example 1,and shown in FIG. 5, the sensing means may be an angular displacementsensor, which is capable of sensing the position of the door or windowto which it is fitted with respect to the corresponding door/windowframe. The sensing means may comprise a potentiometer, which is capableof detecting an angular displacement of the door or window with respectto its frame. The sensing means may comprise a body, one end of thepotentiometer being rigidly secured thereto, for example via a mountingbracket or the like, and an opposite end of the potentiometer beingrotatably secured to the body, for example via a bearing. The bearingmay be a ball bearing, or the like.

The sensing means may comprise an actuating arm, which is connected tothe potentiometer, the actuating arm being arranged to be contacted bythe door or window as it moves between an open and closed configurationwith respect to its corresponding door or window frame. The sensingmeans may comprise biasing means adapted to bias the actuating arm to arest position, which corresponds to the closed configuration of the dooror window. The biasing means may be a spring, for example a torsionspring.

The body, and preferably a lower surface thereof, may comprise a slotalong which the actuating arm may travel as it is urged away from therest position, as the door or window is moved from the closedconfiguration to the open configuration. The slot may be elongate andsubstantially curved, thereby delineating the circumference of asemi-circle.

In use, the sensing means may be attached to a door or window frame orlintel such that, as the door or window is opened, it contacts theactuating arm, and urges the arm away from the door or window frame, thepotentiometer detecting this angular displacement. In use, as theactuating arm moves along the slot, against the biasing force created bythe biasing means, the potentiometer being adapted to detect theposition of the actuating arm, and convert this position into a voltagesignal. The sensing means may comprise means for transmitting thevoltage signal to the control means of the pressurisation apparatus ordepressurisation apparatus, for controlling the air leakage in an escaperoute of the building.

In a second embodiment, the sensing means may comprise an opticalsensor, one example of which is described in Example 2, and shown inFIG. 16. The sensing means may comprise a light emitter adapted to emitlight towards the door or window, and a light detector for detectinglight that is reflected back off the door or window. The light may bevisible light, infrared (IR) or light generated by a laser. In apreferred embodiment, however, the light may be infrared light. Forexample, the wavelength of IR emitted may be about λ=870±70 nm. Thelight emitter and/or light detector may comprise a lens, which may beprotected by an optical cover, which allows efficient transmittance ofthe light therethrough.

The sensing means may be adapted, in use, to determine the position ofthe door or window by calculating the time it takes for the light toreflect back off the door or window onto the detector. The sensing meansmay comprise means for converting this position into a voltage signal.The sensing means may comprise means for transmitting the voltage signalto the control means of the apparatus, for controlling the air leakagein an escape route of the building.

In other embodiments, the sensing means may comprise a Gill Bladesensor, a Magnetopot sensor, a Softpot sensor, a rotary encoder sensoror a laser sensor.

The control means is adapted to control the air leakage in the escaperoute of the building based on the position of the at least one door orwindow detected by the sensing means. It will be appreciated that bycontrolling the air leakage in the escape route, the velocity of air isalso influenced, which in turn will influence the air pressure withinthe escape route.

Thus, the pressurisation apparatus or depressurisation apparatus maycomprise means for creating a pressure differential in the escape routeof the building. For example, the pressure differential may be either apositive or negative pressure in the escape route. Thus, the buildingpressurisation apparatus may be adapted to create a positive pressure inthe escape route, and the building depressurisation apparatus may beadapted to create a negative pressure in the escape route. The pressuredifferential may be created by one or more ventilator fan. The escaperoute may be a stairwell, lobby or corridor of the building, orfire-fighting stairs.

The control means may further comprise a programmable logic controller,which is adapted, in use, to receive data relating to the position ofthe at least one door or window, and trigger the means for creating apressure differential in the escape route of the building. The apparatusmay comprise an inverter for controlling the speed of the means (i.e.fan) for creating a pressure differential in the escape route of thebuilding. The apparatus is preferably adapted to control the velocity ofescaping gas/air/smoke across the face of the door or window in aburning building so that it is at least 2 ms⁻¹, on fire and ground floordoors.

The inventors believe that they are the first to have developed a dooror window position sensor, which can be used for detecting the positionof a door or window with respect to its corresponding door/window frame.

Thus, in a fourth aspect, there is provided a door or window positionsensor for detecting the position of a door or window with respect toits corresponding door/window frame, the sensor comprising apotentiometer, which is capable of detecting angular displacement of thedoor or window with respect to its frame.

The sensor may incorporate the features of sensing means defined in thefirst aspect. The sensor may comprise a body, one end of thepotentiometer being rigidly secured thereto, for example via a mountingbracket or the like, and an opposite end of the potentiometer beingrotatably secured to the body, for example via a bearing. The sensor maycomprise an actuating arm, which is connected to the potentiometer, theactuating arm being arranged to be contacted by the door or window as itmoves between an open and closed configuration with respect to itscorresponding door or window frame. The sensor may comprise biasingmeans adapted to bias the actuating arm towards a rest position, whichcorresponds to the closed configuration of the door or window. Thebiasing means may be a spring, for example a torsion spring. It will beappreciated that the sensor of the fourth aspect may be described asbeing a contact sensor.

In a fifth aspect, there is provided a door or window position sensorfor detecting the position of a door or window with respect to itscorresponding door/window frame, the sensor comprising a light emitteradapted to emit light towards the door or window, and a light detectorfor detecting light that is reflected back off the door or window,wherein, the sensor is adapted, in use, to determine the position of thedoor or window by calculating the time it takes for the light to reflectback off the door or window onto the detector.

The light may be visible light, infrared (IR) or light generated by alaser. Preferably, the light is infrared light. The wavelength of IRemitted may be about λ=870±70 nm. The light emitter and/or lightdetector may comprise a lens, which may be protected by an opticalcover, which allows efficient transmittance of the light therethrough.The sensor may comprise means for converting the position of the door orwindow into a voltage signal, which signal may be used to trigger acontroller. It will be appreciated that the sensor of the fifth aspectmay be described as being a non-contact sensor. The sensor may be usedto detect the position of a hinged or sliding door or window.

In a sixth aspect, there is provided a building pressurisation ordepressurisation apparatus for ventilating a building, the apparatuscomprising the sensor according to either the fourth or fifth aspect.

All of the features described herein (including any accompanying claims,abstract and drawings), and/or all of the steps of any method or processso disclosed, may be combined with any of the above aspects in anycombination, except combinations where at least some of such featuresand/or steps are mutually exclusive.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the accompanying diagrammatic drawings, in which:

FIG. 1 is a schematic side view of a pressurisation system for abuilding;

FIG. 2 is a schematic side view of a depressurisation system for abuilding;

FIG. 3 is a graph showing the linear relationship between the outputvoltage and door angular displacement using a first embodiment of thedoor position sensor of the invention;

FIG. 4 is a flow diagram for a first embodiment of a pressurisation ordepressurisation apparatus according to the invention;

FIG. 5 shows a perspective view of the first embodiment of the doorposition sensor;

FIG. 6a shows a cross-sectional plan view from underneath the firstembodiment of the door sensor, FIG. 6b shows a cross-sectional plan viewof the door sensor from above, FIG. 6c shows a cross-sectional view ofthe front of the sensor, and FIG. 6d shows a plan view of a lid of thesensor;

FIG. 7 shows enlarged views of the various components constituting theinner assembly of the first embodiment of the door sensor. FIG. 7a is aside view of a potentiometer used in the sensor, FIG. 7b is a plan viewof a sensor arm, FIG. 7c is a plan view of a mounting bracket, and FIG.7d is a front view of the mounting bracket. FIG. 7e is a plan view of asupport bracket for the potentiometer (in an unfolded configuration),FIG. 7f is a plan view of the support bracket (in a foldedconfiguration) and a side view of a ball bearing, and FIG. 7g is a sideview of the support bracket;

FIG. 8 is an enlarged perspective view of the first embodiment of thedoor sensor in position attached to the lintel of a fire door;

FIG. 9 is a circuit diagram for the first embodiment of the door sensor;

FIG. 10 is a flow diagram for a second embodiment of a pressurisation ordepressurisation apparatus according to the invention;

FIG. 11 is a graph showing the relationship between the output voltageand door angular displacement using a second embodiment of the doorsensor of the invention;

FIG. 12 is a schematic plan view of the second embodiment of the doorsensor attached to the lintel of a fire door. The Figure indicates theposition of the door at 0°, 30°, 45°, 70° and 90° with respect to thedoor frame;

FIG. 13 is a circuit diagram for the second embodiment of the doorsensor;

FIG. 14a is schematic cross-sectional side view of the second embodimentof the door sensor, and FIG. 14b is a top view of the sensor;

FIG. 15a is a schematic view of the front of the second embodiment ofthe door sensor, and FIG. 15b is a view of the rear of the sensor;

FIG. 16 is a perspective view of the second embodiment of the doorsensor;

FIG. 17 is a front view of a sliding door arrangement with the secondembodiment of the sensor attached to the door jam; and

FIG. 18a shows a Magnetopot door sensor, FIG. 18b shows a Softpot doorsensor, and FIG. 18c shows a Gill Blade sensor.

EXAMPLES

The inventors realised the problems inherent with pressurisation anddepressurisation systems which incorporate differential pressure sensors16 for monitoring and triggering the ventilator fans 22, and havedeveloped several embodiments of a door position (i.e. proximity)sensor, which can be incorporated into the pressurisation system 1 shownin FIG. 1, or the depressurisation system 2 shown in FIG. 2. It shouldbe appreciated that the pressurisation and depressurisation systems 1, 2of the invention, are very similar to the two systems shown in FIGS. 1and 2, but that a door position sensor of the invention, as described indetail below, is used instead of a prior art pressure sensor 16. Eachembodiment of the door position sensor of the invention produces anoutput in the form of 0V to 10 V or 4 mA to 20 mA, which enables it tobe compatible with any industrial or commercial controller. Thefollowing examples describe each embodiment of the door position sensorand how it is incorporated into a pressurisation system 1 ordepressurisation system 2 shown in FIGS. 1 and 2, respectively.

Example 1—Potentiometer-based Door Proximity Sensor (DPS 1)

The first embodiment of door position sensor is a potentiometer-baseddoor sensor 32, and is shown in FIG. 5. The sensor 32 is an angulardisplacement sensor and senses the position of a door 34 to which it isfitted with respect to the corresponding door frame 38 or lintel 36, asshown in FIG. 8. The sensor 32 produces an output in the form of 0V-10Vor 4 mA to 20 mA, as desired. As shown in FIG. 3, the output of thesensor 32 is linear with respect to the position of the door 34, whichmakes its use for controlling a pressurisation system 1 ordepressurisation system 2, both fast and accurate.

FIG. 4 shows a flow diagram for a first embodiment of a pressurisationsystem 1 or depressurisation system 2 of the invention incorporatingsensor 32. When the building 3, 14 is not on fire, the pressurisationsystem 1 or depressurisation system 2 is in standby mode, and the fans22 on the roof of the building are switched off. However, as soon as afire is detected in the building 3, 14, the system 1, 2 is switched on,and the sensors 32 are initiated to detect the position of the doors 34to which they are attached. When a door 34 is closed (i.e. 0° withrespect to the corresponding door frame 38 or lintel 36), the sensor 32signals 0V to the programmable logic controller (PLC, 30), and so theventilator fan 22 remains switched off. However, as soon as the door 34is opened, and an angle is created between the door and the door frame38 or lintel 36, the output voltage will increase linearly, as shown inFIG. 3, causing the ventilator fans 22 to be switched on, therebycreating either a positive pressure in the stairwells 4 of thepressurisation system 1, or a negative pressure in stairwells 4 of thedepressurisation system 2. An algorithm signals an inverter to run thefans 22 at the calculated speed, such that the velocity of air flowingpassed the fire door 34 is fixed about a set-point of at least 2 m/s.The output voltage increases linearly as the door 34 is opened stillfurther until the door 34 reaches a 90° angle with respect to the doorframe 38 or lintel 36, at which point the sensor 32 outputs a maximum of10V. At angles beyond 90°, the output from the sensor 32 will be clampedat 10V as shown in FIG. 3, because the velocity of the air remains thesame across the face of the door 34 beyond 90° with respect to the doorframe 38 or lintel 36.

Sensor Design and Construction (DPS 1)

The sensor 32 is shown most clearly in FIG. 5, and has an outer housing40 made of rigid stainless steel. The housing 40 has an upper surface ortop 96 and a lower surface or base 100, which are inter-connected by acurved sidewall 98. The housing 40 is provided with two flanges 42 oneither side thereof, each flange 42 having a centrally aligned aperture44 through which a screw (not shown) may be passed to secure the sensor32 to a back plate 47 and door frame 38, and in particular the upperlintel 36 of the door 34. An actuating arm 46, which is provided todetect the angular displacement of the door 34 with respect to the doorframe 38 or lintel 36, extends outwardly from the base 100 of thehousing 40.

As shown in FIG. 8, the sensor 32 is attached to the door lintel 36 suchthat, as the door 34 is opened, it contacts the actuating arm 46, andurges the arm 46 away from the door frame 38. The housing 40 of thesensor 32 is designed in such a manner so as to withstand the daily wearand tear to which it will be subjected. The sensor 32 is designed tocover a 180° swing of the door 34, and in order for the sensor 32 tofunction correctly, it is fixed to the lintel 36 such that the mid-pointof the sensor 32 is is aligned with door hinges (not shown). Thisensures that movement of the door 34 is easily and accurately sensed bythe sensor 32. The sensor 32 has been carefully designed so that it iscompact and does not adversely affect the appearance and/or finish ofthe building in which it is used. Since the pressurisation system 1 ordepressurisation system 2 incorporating the sensor 32 is dependant uponthe reliability and performance of the sensor 32, it will be subject toa regular maintenance regime every twelve months.

FIGS. 6 and 7 show the various internal components of the sensor 32.FIGS. 6a and 6b show views of the housing 40 from above and below,respectively, and FIG. 6c shows an internal view of the housing 40 fromthe rear. FIG. 6d shows a plan view of a back plate 47 for the housing40, the back plate 47 having apertures 49 towards each end thereof. Theback plate 47 is secured to the rear of the housing 40 by means ofscrews (not shown) which are passed through apertures 49 in the backplate 47 and apertures 44 in the flanges 42 of the housing 40.

As shown in FIG. 6c , the sensor 32 includes a potentiometer 50, one endof which is secured to the inside of the upper surface 96 of the housing40 by a mounting bracket 52. Detailed illustrations of the potentiometer50 and mounting bracket 52 are shown in FIGS. 7a, 7c and 7d ,respectively. The opposite end of the potentiometer 50 is inserted intoa ball bearing 56, which is supported by a support bracket 54, which issecured to the inside of the base 100 of the sensor housing 40. Detailedillustrations of the ball bearing 56 and the support bracket 54 areshown in FIGS. 7e-g . The actuating arm 46 is connected to thepotentiometer 50 by a sensor arm 58, which is shown in FIG. 7b , and atorsion spring 60 is attached to the sensor arm 58 to bias the sensingarm 58 and the actuating arm 46 to a rest position, when the door 34 isin the closed configuration.

The lower surface of the housing 40 is provided with an elongate curvedslot 48, which delineates the circumference of a semi-circle. Theactuating arm 46 travels along the curved slot 48, as it is urged awayfrom its rest position, as the door 34 is moved from a closedconfiguration to open configuration. With reference to FIG. 6c , theactuating arm 46 would be urged out of the page, as the door 34 opened.As the actuating arm 46 moves around the curved slot 48, against thebiasing force creating by the spring 60, the potentiometer 50 detectsits position, and converts this position into a voltage signal. Thepotentiometer 50 is connected to a printed circuit board (PCB) 62, whichtransmits the voltage signal to the PLC 30, which causes the ventilatorfan 22 of the pressurisation system 1 or depressurisation system to beactivated.

Sensor Circuit (DPS 1)

FIG. 9 shows a schematic diagram of the circuit 64 for sensor 32. Thesensor 32 uses a voltage divider to convert angular displacement intovoltages, and has a variable trimmer resistor which can be used fortuning purposes.

Example 2—Optical Sensor-based Door Proximity Sensor (DPS 2)

Referring FIG. 16, the second embodiment of sensor used in thepressurisation system 1 or depressurisation system 2 of the invention isan optical sensor 66, which has been developed for applications where itis important that the appearance and finish of the building is notcompromised. The optical sensor 66 is small and compact in size, andworks on the principle of reflection of a wavelength (e.g. IR or laser).As shown in FIG. 12, the sensor 66 can be attached to the lintel 36 of ahinged door 34, as with the first embodiment of sensor 32. However, inaddition to hinged doors 34, many modern offices and residentialbuildings have sliding doors 68 to make the most of the available space,as shown in FIG. 17. The optical sensor 66 can be easily fitted todetect the position of any type of sliding door 68, as well as hingeddoors 34.

The optical sensor 66 senses the position of the door 34, 68 andproduces an output in the form of 0-10V or 4 to 20 mA. In oneembodiment, it emits infrared (IR) light onto the door 34, 68, anddetermines its position by calculating the time it takes for the IRlight to reflect back onto the sensor 66. As shown in FIG. 11, at lowangular displacement values with respect to the door frame 38 or lintel36 (i.e. when the door is closed or nearly closed), the sensor's outputis non-linear, but it becomes more linear at higher angulardisplacements (i.e. when the door 34 is open wider). Due to thisnon-linearity at low angles, the control system 30 has to be programmedaccordingly to operate the system reliably.

Referring to FIG. 12, when the door 34 is closed (i.e. at a 0°displacement with respect to the door frame 38 or lintel 36), it willproduce an output signal of 1.8V, which is sent to the PLC 30, whichcauses the ventilator fans 22 to be triggered to run at a lower rate.However, as the door 34 starts is opened, the voltage increases, therebytriggering the fans 22 to be switched on or run at a higher rate. Thevoltage increases further as the door 34 is opened still further, untilthe door 34 reaches an angle of 90°, at which point the sensor 66produces an output voltage of 10V. At angles beyond 90°, the outputvoltage is clamped to 10 V, as shown in FIG. 11. As with the firstembodiment of sensor 32, the voltage is also clamped to boy for thesecond embodiment of sensor 66, because the velocity of the air remainssubstantially constant across the face of the door 34 beyond a 90°displacement.

Sensor Design and Construction (DPS 2)

Referring to FIG. 14a , since the sensor 66 will be subjected to dailywear and tear as well as some extreme conditions, it is provided with anouter housing 72 made of stainless steel. The housing 72 has an uppersurface or top 102, side walls 104, a lower surface or base 106, a frontwall 108 and a rear wall 110. The housing 72 is provided with twoflanges 80 which extend outwards from upper regions of two mutuallyopposing side walls 104. Each flange 80 has an aperture 82 through whicha screw (not shown) may be passed to secure the sensor 66 to a doorframe, in particular the lintel 36 thereof.

The sensor 66 includes an infrared LED emitter 74 and an infrareddetector 76 (both obtained from Sharp), both of which are secured to thebase 106 of the housing 72 by a support bracket 78. The IR emitter 74 isadapted to emit IR radiation towards the door 34, 68, and the IRdetector 76 is arranged to detect the IR waves that are reflected backoff the door 34, 68. The IR emitter 74 and detector 76 each have a lens77, which is protected by an optical cover (not shown), which allowsefficient IR transmittance therethrough. For example, the wavelength ofIR emitted by the LED emitter is λ=870±70 nm. Both faces of the opticalcover are mirror-polished. The IR detector 76 is electrically connected,via wiring 86, to a printed circuit board (PCB) card which is attachedto the 84 via wiring 86, and the output signal that is generated isconnected to the PLC 30 via electric cabling 88.

Sensor Circuit (DPS 2)

In order to work with any industrial controller, an infrared detector 76which generates 0V to 2.5V outputs is used. Referring to FIG. 13, thereis shown a circuit diagram 70 used for the optical sensor 66, which wasspecially designed to convert the output from the IR detector 76 into ananalogue output of 0V to 10V. The DPS2 circuit 70 has two stages. Thefirst stage includes an operational amplifier (OPA350) being connectedin a unity configuration with the high impedance output created by theIR detector 76. This is one of the ways to connect an operationalamplifier to provide unity gain. In the second stage, an operationalamplifier OPA277 is used to convert the voltages into the correctvoltage range of 0V-10 V.

Sensor (DPS2) and Sliding Doors

Referring to FIG. 17, in modern offices and residential buildings,sliding doors 68 are becoming more frequently used, in order to makemost of the available space. Advantageously, the sensor 66 can be easilyfitted to sense the position of any type of sliding door 68.

Example 3—Other Sensor Types

The inventors have also incorporated other types of door proximitysensor into embodiments of the pressurisation system 1 anddepressurisation system 2 of the invention. For example, the sensorswhich have been used include the MagnetoPot 90, SoftPot, Gill BladeSensor, Rotary Encoder and Laser sensor. It was shown that they all hadgood resolution and were very reliable. Magnetopot uses the magneticfield with its wiper movement on a magnetic track varying theresistance, whereas SoftPot uses force and position of the wiper to varythe resistance.

-   -   Softpot 10K by Spectra Symbol, Datasheet        URL:http://docs-europe.electrocomponents.com/webdocs/oe31/0900766b8oe31a61.pdf    -   Magnetopot 10K by Spectra Symbol, Datasheet        URL:http://docs-europe.electrocomponents.com/webdocs/oe31/0900766b8oe31a55.pdf    -   25 mm Blade Sensor by Gill Sensors, Datasheet        URL:http://www.gillsensors.co.uk/content/datasheets/25mm.pdf    -   Retro reflective laser 15 m, P-wired, PNP Datasheet        URL:http://docs-europe.electrocomponents.com/webdocs/oe99/0900766b8oe99453.pdf

CONCLUSIONS

The door proximity sensors 32, 66 described herein are a new beginningin the field of fire engineering and smoke ventilation. Smokeventilation by pressurisation and depressurisation techniques using airpressure sensors have been classified as expensive and difficult, but bythe introduction of the door position sensors 32, 66 of the invention,the prevention of smoke ingress into building escape routes by apressurisation system 1 or a depressurisation system 2 will help toreduce cost, significantly improve the performance and be much easier tocommission. They will enable real-time control of airflow and eliminateover-pressure on doorways, having a very rapid reaction time. It will beappreciated that the position sensors 32, 66 of the invention do notnecessarily need to be used to detect the position of a door 34, 68, andcan also be used with windows. The windows can be located on internalwalls or partitions of the building, their position also influencingingress of smoke into escape routes.

1-37. (canceled)
 38. An apparatus for ventilating an escape route of abuilding, the apparatus comprising sensing means for detecting theposition of a plurality of doors in the escape route of the building,and control means for variably controlling a velocity of air leakage inthe escape route of the building, using a ventilator fan, to be at least2 ms⁻based on the position of the doors detected by the sensing means tomaintain pressure in the escape route at a level sufficient to preventingress of smoke into the escape route from outside of the escape routewhen one or more of the doors are opened, wherein the plurality of doorscomprise sliding doors, wherein the sensing means comprises a pluralityof sensors, each respectively attached to a corresponding one of theplurality of doors, wherein each sensor is capable of sensing theposition of the corresponding door to which it is fitted with respect tothe corresponding door frame, and wherein the ventilator fan is coupledto receive an output of at least one of the sensors so that theventilator fan is switched on when the corresponding door is opened andas soon as an opening is created between the corresponding door and adoor frame in which the door is located.
 39. An apparatus according toclaim 38, wherein the minimum output of the sensors is 0V and themaximum output of the sensors is 10V.
 40. An apparatus according toclaim 38, wherein each of the sensors comprises an optical sensor. 41.An apparatus according to claim 38, wherein the sensing means isconnected to at least one window in the escape route, and wherein thedoor or window is an internal door or window.
 42. An apparatus accordingto claim 38, wherein each of the sensors comprises a light emitteradapted to emit light towards the corresponding door, and a lightdetector for detecting light that is reflected back off thecorresponding door.
 43. An apparatus according to claim 38, wherein thecontrol means comprises means for creating a pressure differential bycontrolling the velocity of the air leakage in the escape route of thebuilding, wherein the pressure differential is created by the ventilatorfan.
 44. An apparatus according to claim 43, wherein the control meansfurther comprises a programmable logic controller, which is adapted, inuse, to receive data relating to the position of at least one of theplurality of doors, and trigger the means for creating the pressuredifferential in the escape route of the building.
 45. An apparatusaccording to claim 38, wherein the apparatus is adapted to control thevelocity of escaping gas/air/smoke across the face of the doors in aburning building so that it is at least 2 ms⁻¹, on fire and ground floordoors.